1. Field of the Invention
The invention relates generally to electrical conductors and, more particularly, to electrical busways. The invention also relates to coupling assemblies for electrical busways.
2. Background Information
Various electrical components are defined by, and subject to, regulatory requirements. For example and without limitation, the Underwriter's Laboratory (UL) defines an “electrical busway”, at UL 857, as a grounded metal enclosure containing factory mounted conductors that are usually copper or aluminum bars, rods, or tubes. Similarly, the National Electric Code (NEC) defines an electrical busway as a grounded metal enclosure containing factory mounted, bare, or insulated conductors, which are usually copper or aluminum bars, rods, or tubes.
Typically, electrical busways include a plurality of electrical conductors (e.g., wires, cables or other suitable conductive members made from an electrically conductive material such as, for example and without limitation, copper or aluminum) that are insulated by a coating, film or sleeve of a non-conductive material (e.g., electrical insulator) and enclosed in a housing, such as an elongated rail structure. The electrical conductors of the electrical busway receive, for example, different phases of alternating current power that power electrical equipment that is electrically connected to the electrical busway.
Different sections of the electrical busway must be suitably electrically connected to bridge a conductive path between those sections. One prior proposal accomplishes this objective by bolting, welding or otherwise suitably electrically and mechanically connecting rigid bus bars between the electrical busway sections. The bus bars electrically interconnect the electrical conductors of one electrical busway section with the corresponding electrical conductors of another, different electrical busway section. However, the bus bars are rigid (e.g., inflexible) and must be permanently deformed to the desired configuration. This limits the number of possible positions in which the various sections of the electrical busway can be arranged and/or rearranged. It also results in the electrical busway occupying a relatively large amount of space, and is labor and cost-intensive.
In an attempt to address the foregoing disadvantages, one prior proposal provides a flexible busway assembly to electrically connect the rigid sections of the electrical busway. However, among other disadvantages, these flexible busway assemblies have termination boxes between the flexible portion and the fixed end portions that mate to the electrical busway sections. Such termination boxes are disadvantageously complex and bulky, thereby inhibiting the full range of flexibility of the flexible assembly. They also necessitate a plurality of separate and independent electrical terminations to effectuate the electrical connection between each electrical conductor and its corresponding terminal of the electrical busway. Specifically, at a minimum, a termination is required between the end of the electrical conductor and the first side of the termination box, and another separate and independent termination is required between the corresponding electrical terminal of the electrical busway and the second side of the termination box. The plurality of separate and independent terminations per electrical conductor are, therefore, independently made on separate discrete segments of the termination box. Each termination point is subject to stress (e.g., a stress concentration point) and, therefore, is susceptible to damage leading to an electrical fault or failure condition. The complex nature of the termination boxes also makes them labor and cost-intensive to manufacture.
Other prior proposals incorporate a flexible non-metallic bellows or housing enclosing the electrical conductors of the flexible busway assembly. However, these prior proposals are limited to applications that do not require a grounded (e.g., without limitation, metal) enclosure around the electrical conductors. Consequently, they are not considered to meet the aforementioned definition of an “electrical busway” and, therefore, are not suitable for certain applications. For example and without limitation, applications that are subject to National Electrical Manufacturers Association (NEMA) standards require the electrical conductors to be enclosed in a grounded metal enclosure, and the busway fittings must be able to carry electrical current up to about 6000 A. Flexible assemblies that do not have a grounded enclosure surrounding the electrical conductors do not satisfy these criteria.
There is, therefore, room for improvement in electrical busways and in coupling assemblies therefor.